This set of Casting Puzzles focuses on “Processing of Thermosetting Plastics – 2”.
1. Thermosetting materials are the polymeric materials which get soften on heating with or without pressure.
a) True
b) False
View Answer
Explanation: Thermosetting materials are the polymeric materials that get permanent hardness once the heat is given to the material. These are the polymers which require heat and pressure to mould them into shape. These polymers cannot be re-softened once they are set and hardened by heat.
2. Thermosetting plastics are generally used for making products of high strength and rigidness.
a) True
b) False
View Answer
Explanation: Thermosetting polymers basically involve cross-linked molecular structure and thus it is ideal for making products which demand rigidity and strength. Due to cross linking in thermosetting polymers, these are made hard, tough, and cannot be re-moulded as thermoplastic polymers.
3. Which of the following types of molecular structure present in thermosetting polymers?
a) Linear polymers
b) Branched polymers
c) Cross-linked polymers
d) Network polymers
View Answer
Explanation: Cross-linked polymers are described by adjacent linear chains that are brought one to another at several locations by covalent bonds. Cross linking is completed by a non-reversible chemical reaction. Often, cross-linking is finished by additive atoms which are covalently bonded to the chains in the thermosetting polymers.
4. Polyurethanes plastics can be made in flexible foams even after belonging to thermosetting polymers.
a) True
b) False
View Answer
Explanation: Polyurethane plastics are belonged to the thermosetting plastics or polymers. Polyurethane is the only polymer that can be formed in both rigid and flexible foams. The flexible polyurethane foam is generally used in the manufacturing of mattresses, carpets and furniture. And the rigid polyurethane foam is used in making of chairs and mirror frames.
5. Polyethylene, polypropylene and polyvinyl chloride (PVC) are the main example of thermosetting polymers.
a) True
b) False
View Answer
Explanation: Polyethylene, polypropylene and polyvinyl chloride (PVC) are basically examples of thermoplastics material. And thermosetting material’s example includes polyurethanes, polyesters, epoxy resins and phenol resins which are used for manufacturing of aircraft parts, tires and auto parts.
6. Thermosetting plastics like epoxies can be used for filament wound rocket motor casings in missiles by combining with glass fibers.
a) True
b) False
View Answer
Explanation: Epoxies can be used in various ways. In adding with glass fibers, it is capable of making composites that are of high strength and heat resistant. These composites are basically used for making motor casings in missiles, aircraft parts, fixtures etc. Epoxies are also found in industrial equipment and in protective coatings of appliances.
7. Polyurethane plastics are highly reactive to chemical compounds due to lack of elasticity in these plastics.
a) True
b) False
View Answer
Explanation: Polyurethane plastics come in the category of thermosetting plastics. In this type of plastics, elasticity is generally very high. Due to this property of high elasticity, it can be used in decorative and protective coatings. The high elasticity also makes these polyurethane polymers highly resistant to any chemical attack.
8. Phenolic plastics can also be used as binder for holding plies of wood in making of plywood.
a) True
b) False
View Answer
Explanation: Phenolic plastics or polymers are belongs to thermosetting plastics. These are the special type of resins which can be used in potting compounds, casting resins, and laminating resins. They can also be used in making of electrical equipment. Phenolic plastics are very popular binders for holding plies of wood in manufacturing of plywood.
9. Thermosetting plastics can be used for manufacturing of windshield for airplane.
a) True
b) False
View Answer
Explanation: For the manufacturing of windshield for airplane, poly-acrylics plastics are used which basically belongs to the group of thermoplastics. Poly-acrylics are transparent, high tough in nature and can be easily shaped in any form. Due to such properties of this material, it is widely used for making of windshields for airplane.
10. Mechanical properties of any plastics are mainly dependent on the temperature, force and time of load applied.
a) True
b) False
View Answer
Explanation: Mechanical properties relate to movement or breakage of the polymer due to some mechanical variation such as application of load. Mechanical properties are mainly dependent on the temperature, force or load applied, and the duration of time the force is applied. It can also be affected by ultra-violet radiation when used outside.
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